Printing by vapor propulsion

ABSTRACT

A liquid ink layer is formed on the surface of a transparent substrate. The ink layer is exposed through the substrate to high energy radiation causing exposed ink areas to move to a receiver sheet. It is believed that the ink is transferred by the rapid expansion of vapor.

United States Patent Gundlac'h [15] 3,655,379 [451 Apr. 11, 1972 [54]PRINTING BY VAPOR PROPULSION [72] Inventor: Robert W. Gundlach, Victor,NY. A

[73] Assignee: Xerox Corporation, Rochester, N.Y.

[22] Filed: Oct. 29, 1969 [21 1. Appl. No.: 872,135

3,207,602 9/1965 Shely 3,280,735 10/1966 Clark et a1. 3,360,367 12/1967Stricklin ..96/27 X 3,408,216 10/1968 Mott et a1. ..117/37 X 3,446,6175/1969 Stricklin ..96/ 27 3,455,687 7/1969 Holstead et a1. ....250/65.1X

3,490,371 l/1970 Games ..250/65.1 X

OTHER PUBLICATIONS Rositon et al., IBM Technical Disc. Bull, Vol. 7, N0.3, Aug. 1964, page 224.

Primary Examiner-John T. Goolkasian Assistant Examiner.loseph C. Gil

Attorney-James .1. Ralabate, Richard A. Tomlin and David C.

Petre [5 7] ABSTRACT A liquid ink layer is formed on the surface of atransparent substrate. The ink layer is exposed through the substrate tohigh energy radiation causing exposed ink areas to move to a receiversheet. 1t isbelieved that the ink is' transferred by the rapid expansionof vapor.

8 Claims, 2 Drawing Figures PATENTEDAPR H I972 INVENTOR ROBERT w.GUNDLACH fiww ATTORNEY PRINTING BY VAPOR PROPULSION BACKGROUND OF THEINVENTION This invention relates in general to image formation and morespecifically to the formation of images by the transfer of liquid from adonor member to a receiver member in response.

to imagewise high energy electromagnetic radiation.

Many methods are known for producing visible images including printingand photographic methods where the color of a light sensitive chemicalis changed by the action of light. Other methods of forming a visibleimage are known where light is used to alter the hardness, tackiness,solvent resistance, or ink receptivity of a suitable material. Othermethods include electrostatic methods where an electrostatic chargepattern is formed on the surface of a material and is developed byelectroscopic material. Further methods are known where high energylight is used to cause the evaporation of a material in imageconfiguration from a donor sheet with subsequent condensation in imageconfiguration on a receiver sheet. An additional process is shown inU.S. Pat. No. 2,503,759 to A. Murray in which a material is evaporatedfrom a substrate in image configuration leaving behind a positive image.The above processes all require complex image forming and developingsteps or the evaporation of a material to form a final print.

Another method of forming an image is disclosed in copending applicationSer. No. 783,059 filed Dec. 11, 1968 by W. E. L. Haas et al. in which alayer of radiation absorbing particles is placed on a donor sheet andexposed to an imagewise pattern of high intensity short durationradiation which propells the particles from the donor sheet in animagewise pattern to a receiving sheet. The donor layers used in thisprocess are, however, difficult to reconstitute and are disposed.

SUMMARY OF THE INVENTION It is an object of this invention to provide animaging system which overcomes the above mentioned disadvantages.

It is another object of this invention to provide a relatively simpleimaging system.

It is another object of this invention to provide an imaging systemwhich requires no chemical developing step.

It is another object of this invention to provide an imaging systemwhich does not require complex chemicals or charge patterns.

It is another object of this invention to provide a method for printingimages without the necessity for preparing printing plates.

The above objects and others are accomplished in accordance with thisinvention by providing a'layer of liquid ink on the surface of atransparent member. A receiver sheet is placed close to the liquidlayer. The liquid layer is then exposed to high energy electromagneticradiation in image configuration. It has been found that when thesesteps are completed the liquid in light struck areas jumps across a gapto the receiver sheet in image configuration. The image on the receiversheet may then be fixed by allowing the ink to dry or the receiver sheetmay be somewhat porous allowing the liquid to permeate therein. Byexposing the liquid layer to radiation projected through a negativetransparency a positive image may be formed on the receiver sheet. In apreferred embodiment the substrate on which the liquid layer is formedis in the form of a gravure or grooved plate. The grooves or cups arefilled with the liquid and the raised areas which contact the receiverare substantially free of ink. The receiver sheet may then be placed incontact with the raised areas of the gravure or grooved plate. Sharperimages are obtained when the liquid layer is in the ,form of a series ofminute, discrete pools rather than in the form of a uniform liquidlayer. A further advantage exists in that since the receiver sheet is incontact with the raised areas of the plate it is almost in contact withthe liquid thereby requiring less light energy to move the liquid to thereceiver sheet than would be required if the receiver sheet were placedat some distance from the liquid layer and also provides sharper images.

Although the exact mechanism which causes the layer to be transferred tothe receiver sheet is not known, apparently small pockets of vapor areformed in image areas by the conversion of radiant energy to heat energyupon absorption near the interface between the transparent member andthe liquid layer. The rapid expansion of these vapor pockets propels theliquid away from the transparent member. It has been found that imagesmay be formed across as much as a V; inch gap. Since evaporation of morethan a very small'fraction of the liquid layer is not required to causetransfer, the energy requirements are much less than for those systemswhich require the evaporation and condensation of an entire layer.

It is desirable to use a relatively short period of illumination tocause transfer. The energy provided by an extended low level ofillumination would tend to be dissipated by conduction to the substrateor surrounding ink layer. A preferred illumination would have an energyof less than about 1.0 joules/cm. for a time not greater than about 10sec., depending on the thickness of the'layer, the nature of the layer,the gap to be traversed and whether blowing agents are incorporated inthe layer. For example, where the illumination time is reduced to about4 X 10 seconds an energy level of about 0.3 joules/cm. is sufficient.

Images may be formed in any color depending only on the color of theliquid ink used. Further, full color images may be prepared by usingcolor separation transparencies and superimpo sing a succession ofcolored images on a single receiver sheet.

Fixing of the image produced may be aided by utilizing a liquid ink inwhich a paraffin or wax-like material has been dissolved. On evaporationof the liquid component the waxlike material will form a binder for thefinal image. Or the liquid layer may be a material which is a liquid atelevated temperatures and where fixing is accomplished by allowing theimage to cool.

The liquid layer may be a dispersion, a suspension, or a solution andmay be of one or more phases. The liquid layer may be a printing inksuch as a mixture of finely divided pigment such as carbon blacksuspended in a drying oil such as heatbodied linseed oil. Alkyds,phenol-formaldehyde or other synthetic resins and cobalt, manganese, andlead soaps may be added to achieve rapid drying by oxidation andpolymerization. Inks which dry by evaporation of a volatile solvent suchas mineral oil may be used. For colored inks pigmented or dyed inks suchas inks containing chrome yellows, benzidine yellows or lithol reds maybe used.

A preferred liquid layer comprises a suspension of carbon black inisopropyl alcohol. This liquid layer is preferred because it gives darkblack images and dries rapidly.

To aid transfer blowing agents whether gaseous, liquid or solid may beincorporated into the inks. Blowing agents or foaming agents are thosematerials which produce an inert gas such as nitrogen or carbon dioxidewhen heated. Typical blowing agents include pentane, hexane, isohexane,methylene chloride and trichlorotrifluoroethane.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages of this improved methodof imaging will become apparent upon consideration of the detaileddisclosure of the invention, especially when taken in conjunction withthe accompanying drawings wherein:

FIG. 1 shows a side view of a simple exemplary system for carrying outthe process of this invention wherein a transparency is placed on theinside of a transparent drum and exposure is made through thetransparency. The thickness of the liquid ink layer has been greatlyexaggerated for purposes of clarity.

FIG. 2 shows an enlarged cross sectional side view of an exemplaryimaging station in accordance with this invention. Sizes and distanceshave been distorted for purposes of clarity.

Referring now to FIG. 1 there is seen transparent drum 1 which may befor example glass, plastic, or other suitable transparent material.Liquid ink 2 is applied to the surface of drum 1 by applicator roller 3.The thickness and uniformity of liquid ink 2 is controlled by flexibledoctor blade 4. A transparency 5 is placed on the inside of transparentdrum 1. This arrangement is exemplary, many other arrangements wouldprovide similar results. Preferably the surface of drum 1 is in the formof a gravure or grooved plate, which provides cleaner separation betweenimage and non-image areas. Light source 7 which may be, for example, alaser or other collimated light source and lens 9 are used to provide ahigh energy source of radiation which is focused in a fine line on theinner surface of liquid ink layer 2. In dark areas of transparency 5sufficient energy is absorbed to prevent transfer of ink layer 2. Intransparent areas of transparency 5 sufficient energy is imparted toliquid ink 2 to cause it to move across the gap to receiver sheet whichmay be, for example, paper. Receiver sheet 15 in this exemplary instanceis entrained over drum 17. A positive image 19, that is the image whichhas light and dark areas corresponding to light and dark areas oftransparency 5 is formed on drum 1. This image may be transferred andretained where desired. Negative image 21, that is the image which hasdark areas corresponding to light areas of transparency 5 is formed onthe surface of receiver sheet 15.

Referring now to FIG. 2 there is seen a greatly enlarged cross sectionalarea of a preferred imaging station for use in this invention.Transparent donor layer 23 is provided with small grooves or dimples 25.Grooves 25 are filled with liquid ink 26 and doctored such that whenreceiving member 27 is placed in contact with donor 23 no ink transferswithout the application of light 29 which is focused to a fine line bycylindrical lens 30. Transparency 33 having image areas 34 providesimagewise illumination of the donor member 23.

DESCRIPTION OF PREFERRED EMBODIMENTS The following examples furtherspecifically illustrate the improved imaging process of this invention.All parts and percentages are based on weight unless otherwise stated.The following examples are intended to illustrate various preferredembodiments of the improved imaging process.

EXAMPLE I Approximately 50 parts by weight of finely divided carbonblack is dispersed in about 50 parts isopropanol. A glass slide isprepared by placing 3 mil tape on its ends. The space between the tapeis coated with about a 25 microns thick layer of the suspension. Theslide is placed face down over a piece of paper. The tape provides a gapbetween the ink and the paper of about 2 mils. A stencil is placed onthe top side of the glass. The liquid ink is illuminated through thestencil and glass slide by a flash from a gas discharge lamp whichprovides an energy level of about 0.4 joules/cm. over a time of about 3X 10 sec. On separation of the glass slide and paper receiver an imageis found on the paper corresponding to the stencil.

EXAMPLE II The experiment of Example I is repeated except that the glassslide is placed ink side up, the paper is placed over the slide and thestencil is placed under the slide. That is the paper, slide, stencilcombination of Example I is turned over. The ink is exposed through thestencil as in Example I. An image corresponding to the stencil is againfound on the paper. This demonstrates that the ink may be driven againstthe force of gravity.

EXAMPLE III The experiment of Example I is repeated except that thecarbon black is replaced by a carbon black pigmented copolymer ofpolystyrene and n-butylmethacrylate available as xerographic toner. Theimage is fixed by application of heat providing a rub'resistant highquality image.

EXAMPLE IV A glass plate is provided having about I50 grooves to thelinear inch both horizontally and vertically. The grooves areapproximately 3 mils deep providing a raised area of about l0 percent ofthe total area. The plate is inked with the ink of Example I using adoctor blade which provides an ink level about /2 mil below the level ofthe raised areas. A smooth surfaced paper receiver sheet is placed incontact with the plate. The liquid ink is illuminated through a stencilas in Example I providing an image on the receiver paper. This image iscompared to the image prepared in Example I and found to be of higherresolution evidencing cleaner separation between illuminated andnon-illuminated areas.

EXAMPLE V In this Example an opaque black donor member is used and theradiation is directed through the receiver sheet and ink layer beforebeing converted to heat energy by the black donor member. A donor memberis' made by forming about 200 parallel grooves per linear inch in blackanodized aluminum and at about a right angle to the parallel groovesanother about 200 parallel grooves per linear inch are made providing adonor member similar to that of Example IV. The grooves are about 1 mildeep. The inking is doctored so that a /2 mil deep layer of ink isformed in the grooves. A translucent receiver sheet is placed over theinked aluminum donor plate. Illumination is made through a templateusing infrared radiation of about 0.4 joules/cm. 2 for about 4 X 10seconds providing an image on the surface of the translucent paper. A

and the image transferred to paper if desired.

EXAMPLES Vl-IX The experiments of Examples I-IV are repeated using anillumination of 0.2 joules/cm. for l X 10 seconds. The images are foundnot to be of as high quality as those of Examples I-IV.

Although specific components and proportions have been stated in theabove description of preferred embodiments of the invention othertypical materials as listed above, where suitable, may be used withsimilar results. In addition, other materials may be added to the ink tosynergize, enhance or otherwise modify the properties of the ink. Forexample, polymerization initiators activated by light may be added toassist the fixing of the final image.

Other modifications and ramifications of the present invention willoccur to those skilled in the art upon a reading of the disclosure.These are intended to be included within the scope of this invention.

What is claimed is:

1. An imaging process comprising:

a. providing a donor member;

b. applying a layer of a liquid ink to said donor member;

and,

c. exposing at least a portion of the interface of said liquid ink layerand said donor member to a pattern of electromagnetic radiation until animage is formed by the vapor propulsion of liquid from said donormember.

2. The process of claim 1 including the additional step of:

(1. providing a receiver member to intercept the ink which is removedfrom said donor member at least prior to or con currently with step (c).

3. The process of claim 1 wherein said electromagnetic radiation iscollimated light.

4. The process of claim 1 wherein said donor member comprises atransparent member having recessed areas.

5. The process of claim 1 wherein said donor member comprises an opaquemember having recessed areas.

6. The process of claim 1 wherein said ink comprises finely dividedparticles of pigment dispersed in a liquid.

7. The process of claim 1 wherein said ink comprises a dye solution.

8. The method of claim 1 wherein said donor member is transparent andsaid radiation is projected through said transparent donor member.

2. The process of claim 1 including the additional step of: d. providinga receiver member to intercept the ink which is removed from said donormember at least prior to or concurrently with step (c).
 3. The processof claim 1 wherein said electromagnetic radiation is collimated light.4. The process of claim 1 wherein said donor member comprises atransparent member having recessed areas.
 5. The process of claim 1wherein said donor member comprises an opaque member having recessedareas.
 6. The process of claim 1 wherein said ink comprises finelydivided particles of pigment dispersed in a liquid.
 7. The process ofclaim 1 wherein said ink comprises a dye solution.
 8. The method ofclaim 1 wherein said donor member is transparent and said radiation isprojected through said transparent donor member.